Method and device for the manufacture of electron tubes

ABSTRACT

A METHOD AND APPARATUS FOR MANUFACTURING, WITHIN AN EVACUATED HOUSING, RADIATION SENSITIVE ELECTRON TUBES COMPRISING VAPOR-DEPOSITING A PLURALITY OF WINDOW SECTIONS OF THE ENVELOPE OF THE ELECTRON TUBE IN SEQUENCE, CHECKING FOR DEFECTS AFTER A LAYER IS FORMED ON EACH WINDOW SECTION UNTIL A WINDOW WITHOUT DEFECTS IS FOUND, AND THEN SEALING THIS WINDOW TO THE GLASS ENVELOPE COMPRISING THE ELEMENTS OF THE ELECTRON TUBE.

N 7, 1972 JEANCHARLES VIEIRS E 3,703,212

METHOD AND DEVICE FOR- THE MANUFACTURE OF ELECTRON TUBES Filed July 15,1969 .2 Sheets-Sheet l mm 'r 1 i 6 E 15 I F E 1 E Z i 5 j 1 I 1 C I v 1w/ i g l 14 i P 8 n g 3 i i i l III II I I l I 9 I k g l Fug] INVENTORfiJEAN C. VIERS BY ROBERT P. JAURE 9 1972 JEAN-CHARLES VIERS ETAL ,702,

METHOD AND DEVICE FOR THE MANUFACTURE OF ELECTRON TUBES Filed July 15.1969 .2 Sheets-Sham 2 INVENTORJ JEAN c. VIERS By ROBERT P. JAURE UnitedStates Patent 3,702,212 METHOD AND DEVICE FOR THE MANUFACTURE OFELECTRON TUBES Jean-Charles Viers, Brive-la-Gaillarde, and Robert PierreJaure, Rolland-Brive-la-Gaillarde, France, assignors to US. PhilipsCorporation, New York, N.Y.

Filed July 15, 1969, Ser. No. 841,751 Claims priority, applicationgrance, July 16, 1968,

Int. Cl. H015 9/38, 17/36 U.S. Cl. 316-3 7 Claims ABSTRACT OF THEDISCLOSURE This invention relates to a method and device for themanufacture of electron tubes, particularly tubes comprising elementshaving a sensitive layer.

It is known to assemble and treat components of an electron tube in avacuum space and to seal it in the same space by using pressure and/ orheat. In this manner tubes Without exhaust tube are obtained, which havecomparatively constant characteristics owing to their construction andseal in the same atmosphere.

The method disclosed in British patent specification No. 871,206 of Mar,25, 1959 permits activating photocathodes of a cascade-type imageintensifier, mounting the photo-cathodes in the glass envelope andsealing the latter in the same space. The photo-cathodes fixed to theinternal surface of a large-diameter conical support are introduced byrotation of the cone about its tip into an activating furnace and thenbrought in front of the opening of the glass envelope, where a simpledevice permits introducing and disposing them in place.

The part of the glass envelope intended to receive the treated elementsis placed in a mount integral with the movable part of a screw press,whereas the part intended to seal the tube is placed on the stationarypart of the press. The two metal rings forming the edges of the twoparts of the envelope are cold-weldedto each other under a predeterminedpressure.

This manufacturing method permits eliminating given causes of pollutioninvolved in carrying out the activation and the assembling in separatespaces. The simplicity of the activating operation consisting in asingle heating operation permits using the device described. However,the required dimensions of the support assembly are fairly large andpartly necessitated by the conical support and its way of operating.Therefore, the volume of the vacuum bell in which the various operationsare carried out, is large, which involves a comparatively long time forexhausting and degassing, so that the efliciency is limited.

These disadvantages are partly eliminated by the device disclosed inFrench patent specification 1,434,291 of Feb. 23, 1965. The method alsodisclosed in said patent specification permits manufacturingphoto-multipliers. These tubes comprise a sensitive layer deposited onthe input face for the radiation.

The glass envelope comprising the mechanical elements of the tube isinserted into a device for pressurized closure similar to that describedabove, arranged in an exhaustable space, while the envelope portionforming the 3,702,212 Patented Nov. 7, 1972 window is disposed oppositethe envelope against the stationary part of the press. After asatisfactory vacuum is attained the sensitive layer is formed in situ bybringing one or more Vaporizers above the window. The evaporation timesare adjusted so that a layer of desired characteristics is obtained.

Before the tube is closed, the layer is checked. If the measures do notyield results corresponding to the desired characteristics, theoperation is stopped. It is then neces sary to allow air to enter inorder to be able to withdraw the bell and to replace the defiectivewindow. Then the sequence of operation is repeated.

When it is necessary to change the Window in this way, the loss of timeis very considerable, Moreover, the comparatively great displacement ofthe Vaporizers is critical on account of the electric connections.

The method and the device in accordance with the invention are relatedto the methods and devices of the type described above and eliminate thedisadvantages involved in an accidental formation of a defectivesensitive layer, since the formation of a new layer has only littleinfluence on the rhythm of the production.

The method according to the invention for the manufacture of electrontubes in which a sensitive layer is formed in the same space where thetube is exhausted and sealed, is mainly characterized in that theformation of the sensitive layer is carried out after a support isarranged above one or more stationary Vaporizers, said support providedwith the sensitive layer being located in front of a checking devicepermitting defining the characteristics of the layer prior to itsincorporation in the structure of the tube, while a further sensitivelayer is formed on a further support also located in the space only whenthe first layer is found to be defective.

According to the invention the device for the manufacture of electrontubes comprising a housing containing a vacuum, a device for holding andsealing by pressure an electron tube, a vaporizer to form the sensitivelayer on a support, is mainly characterized in that the vacuum comprisesat least two supports to form the sensitive layer, which supports areindependent of each other.

The invention will be better understood with reference to theaccompanying drawing, which is given by way of non-limiting example.

FIG. 1 is a general view of the device in accordance with the inventionillustrating the positions of the vaporizers and a target support.

FIG. 2 is a plan view of the device.

' FIG. 1 shows the whole system for treating and sealing. Beneath thevacuum bell 10 is arranged an auxiliary member 11 comprising theelectric through-connections for feeding the vacuum pump, the vaporizersand the checking devices for the sensitive layer; at 12 is arranged thejack-screw integral with the movable portion 14 of the press for weldingtogether the parts of the tube in the cold state and at 9 is arrangedthe vacuum channel between the space and the secondary pump.

The press for sealing the tube comprises (see FIG. 1) two columns 1firmly secured to the base plate of the housing containing a vacuum,while the piston of the screw 12 passes through the plate viavacuum-tight bellows 3 and bears on a transverse member 14 adapted toslide along the two columns 1; a support 2, secured to the transversemember 14, receives the glass envelope of the electron tube comprisingalready the mechanical components. At the ends of the two columns 1 atransverse member 15 serves as a stop and withholds the front part 5 ofthe tube, so that the two tube portions can be sealed together bypressure.

This front part of the tube 5, forming the window, is fixed prior to itsdisposition on the transverse member 15,

to a support adapted to move around a shaft 6, whose rotation iscontrolled at 7 from without the vacuum space with the aid of amechanical device 8 or the like (FIGS. 1 and 2), which is vacuum-tight.

The vaporizer 4 is secured to the support 2 of the electron tube,whereas the support of the window 5 is moved to a position above thevaporizer. The distance between the window and the vaporizer may bevaried by actuating the screw and since the vacuum space comprises atleast two window supports, the axes of the window supports are locatedeach on one side of the vaporizer so that the distances 'between theaxes of the supports and the centre of the vaporizer and the centre ofthe stop of the press are equal.

The method in accordance with the invention comprises the followingsteps: the vacuum bell is lifted from the base plate and a window isplaced on each of the supports (adapted to move about the shafts 6 and16) (FIG. 2). The vaporizer 4 is filled with the substance intended toform the sensitive layer and after the tube portion to be sealed isplaced on the support 2, the bell is put on the base plate and exhaustedthrough the channel 9. The diameter of this channel is very large ascompared with the dimension of the base plate; since, in addition, thesecondary pump directly communicates with this channel, the efiiciencyis at a maximum so that the exhaust time is comparatively short. Duringthe exhaust operation the windows are in extreme positions 17 and 17'.

When the desired vacuum is attained, one of the windows is moved intothe position 18 directly above the vaporizer 4, after which thesensitive layer is formed by the evaporation of the various substancescontained in the vaporizer. For the duration of this operation up to theend the formation of this layer is checked so that in the event ofdefects the process can be stopped and the window can be replaced by asecond window for a new formation without the need for opening thevacuum space.

The disposition of the mechanical elements, i.e. the eccentric positionof the jack-screw, leaves an important part of the base plate unoccupiedso that direct pumping can be carried out with a minimum loss in eachstroke.

Moreover, the disposition of the pumping gear permits of minimizing theheight of the part 11 (FIG. 1), which now serves only for the variouselectric through-connections. a

The disposition of at least two independent window supports providesconsiderable advantages:

the volume of the vacuum space is smaller than in the case of a commonsupport, sparing of at least one window ready for use in the event of adefect of the first window avoids the quite considerable loss of timeinvolved in the necessity of breaking the vacuum in the space forexchanging the window and for reobtaining the operative conditions;

the time of pumping and degassing is fairly long and it is often onlypossible to manufacture one tube a day, when the operation is successfulfrom the start.

What is claimed is:

1. A method of manufacturing radiation sensitive tubes from envelopeshaving base and window portions comprising positioning said windowportion at a first position within an evacuated housing, forming a firstsensitive layer upon said window portion, checking for defects in thefirst sensitive layer while said window portion is in said firstposition, moving said window portion to a second position within saidevacuated housing, sealing said window portion to said base portion ifsaid sensitive layer is free of defects without interrupting the vacuumin said housing, and forming a further sensitive layer on another windowportion at said first position only when said first sensitive layer isfound to be defective.

2. Apparatus for manufacturing radiation sensitive electron tubes fromenvelopes having a base portion and a window portion with a sensitivelayer comprising an evacuated housing, supports for positioning saidwindow portions in first and second operating positions within saidhousing, at least one vaporizer within said housing to form thesensitive layer on said window portion while said window portion is insaid first position, means within said housing for checking for defectsin said sensitive layer while at said first position, and a devicewithin said housing for holding said base portion in said secondposition and sealing said window portion to said base portion if saidsensitive layer is free of defects, said vaporizer forming a furthersensitive layer on another window portion at said first position onlywhen said first sensitive layer is found to be defective.

3. Apparatus for manufacturing radiation sensitive electron tubes asclaimed in claim 2 wherein said holding and sealing device comprisesmovable and stationary sections of a press, said stationary part havingrotatable members supporting said window portions on each side of saidvaporizer to make the distances from the rotatable members to thecenters of said vaporizer and the center of said press equal.

4. Apparatus for manufacturing radiation sensitive electron tubes asclaimed in claim 3 wherein the center of said window portion coincideswith the center of said vaporizer when said vaporizer is depositing saidsensitive layer and with the center of said press when sealing saidsupport to the glass envelope comprising the elements 0 said electrontube.

5. Apparatus for manufacturing radiation sensitive electron t-ubes asclaimed in claim 2 further comprising means outside said housing forindependently positioning said window portions and operating saidholding and sealing device.

6. Apparatus for manufacturing radiation sensitive electron tubes asclaimed in claim 2 further comprising external means for evacuating saidhousing.

7. Apparatus for manufacturing radiation sensitive electron tubes asclaimed in claim 6 wherein said evacuated housing provides for directpumping with a minimum loss by said external means for evacuating saidhousing.

References Cited UNITED STATES PATENTS 5/1967 Keller et a1 3163 2/ 1968Yoshida et a1. 3163 US. Cl. X.R. 3163l

